SQL to concatenate many rows into a single string

I used this SQL script to convert multiple returned rows into a single text string in SQL Server 2008.
SELECT REPLACE(
(SELECT CASE TBL.DayNumber
WHEN 1 THEN 'Sun'
WHEN 2 THEN 'Mon'
WHEN 3 THEN 'Tue'
WHEN 4 THEN 'Wed'
WHEN 5 THEN 'Thu'
WHEN 6 THEN 'Fri'
WHEN 7 THEN 'Sat'
ELSE NULL
END AS 'data()' 
FROM [dbo].[MyTableName] TBL
FOR XML PATH (''))
, ' ', ',') AS CommaDelimDayNames

This will convert:
Id          DayNumber
----------- --------------------
77          4
77          5
77          6

into:
Id          CommaDelimDayNames
----------- --------------------
77          Wed,Thu,Fri


As usual I had inspiration from the wonderful stackoverflow, in particular Diwakar's answer:
http://stackoverflow.com/questions/194852/concatenate-many-rows-into-a-single-text-string/5580166#5580166
This has the answer:

REPLACE((select FName AS 'data()'  from NameList  for xml path('')), ' ', ', ')